T E Schmitz <mailreg@numerixtechnology.de> writes:
> Tom Lane wrote:
>> Whatever you were reading had it pretty badly garbled :-(
> I just dug out the PostgreSQL book again because I thought I might've
> garbled it:
> Quote: "PostgreSQL will not index NULL values. Because an index will
> never include NULL values, it cannot be used to satisfy the ORDER BY
> clause of a query that returns all rows in a table."
[ shrug ] It's wrong on both counts, and has been since (checks CVS) 1997.
What book is that anyway?
There is a related statement that is still true: "WHERE x IS NULL"
(or NOT NULL) clauses are not indexscannable. This is a shortcoming of
the planner-to-index-access-method interface, though, not a question of
whether the index can store NULLs.
regards, tom lane
